Path analysis and the relative importance of male-female conflict, female choice and male-male competition in water striders

Andrew Sih, Michael Lauer, James J. Krupa

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78 Scopus citations

Abstract

Three major behavioural mechanisms underlying sexual selection in many systems are male-male competition, female choice and male-female conflict. We used path analysis to evaluate the relative importance of these mechanisms in generating sexual selection on a suite of male traits in the stream-dwelling water strider, Aquarius remigis. To gather data for the analysis, we quantified the morphology (total length, limb length, forefemur width, genital length), behaviour (activity), mating frequency, mean mating duration and overall mating success of 96 adult males over a 10-day period. Males varied considerably in mating success. Over the 10 days, individual males mated 0-14 times, spending 0-67% of their time in copula. Path analysis showed that male-male competition was important in favouring larger males with longer limbs that tended to be more active. Active males should encounter females more frequently. In water striders, almost all male-female encounters result in intense premating struggles pitting female resistance to mating against male insistence. This male-female conflict favoured larger males with longer genitalia. These traits help males overcome female resistance. Female choice was expressed via female-controlled variation in mate-guarding durations. Female choice favoured smaller males perhaps because they are lighter, less expensive shields against harassment by other males. Male size thus affected mating success via all three behavioural mechanisms. Weak, overall sexual selection favouring larger males was the product of conflicting effects: male-female conflict strongly favouring larger males and male-male competition weakly favouring larger males, offset by female choice favouring smaller males. Separate analyses for warmer versus colder days showed that on colder days (daily high below 20°C), male-male competition was the main mechanism generating variation in mating frequency, while on warmer days, both male-male competition and male-female conflict were important.

Original languageEnglish
Pages (from-to)1079-1089
Number of pages11
JournalAnimal Behaviour
Volume63
Issue number6
DOIs
StatePublished - 2002

Bibliographical note

Funding Information:
We thank Kris Haskins, Tim Sparkes, Andy Storfer and Dave Wooster for help in collecting data, and John Hammond, Tom McCarthy and two anonymous referees for comments on the manuscript. Many of our ideas on multiple, conflicting behavioural mechanisms emerged from conversations with Alison Craig, Marie-Sylvie Baltus-Sih, Loric Sih and Maya and Caleb Craig-Lauer. This work was supported by National Science Foundation grants (IBN 9514142 and IBN 0078033) to A. Sih and J. J. Krupa.

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Animal Science and Zoology

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